Simultaneous radio detection and bearing system

ABSTRACT

Provided is a simultaneous radio detection and bearing system. More specifically, the radio detection and bearing system includes an RF conditioning subsystem having a plurality of First Frequency Range and Second Frequency Range signal receiving channels. The RF conditioning subsystem operable to combine First Frequency Range and Second Frequency Range signals as a first internal data stream. A coherent multi-channel digitizer subsystem is coupled to the RF conditioning system, the coherent multi-channel digitizer subsystem operable to generate a time domain snapshot of the first internal data stream. An audio recording subsystem is also coupled to the RF conditioning subsystem. A processor is coupled to the coherent multi-channel digitizer subsystem and the audio recording subsystem. The processor is operable to transform the time domain snapshot to a frequency spectrum and identify at least one signal above a threshold at a determined frequency, determine the bearing of the signal, and provide the determined frequency to the audio recording subsystem. The audio subsystem contemporaneously records the signal upon the determined frequency. An associated method of radio detection and bearing determination is also provided.

This invention was made with Government support under contract No.GS23F0264M awarded by the National Security Agency. The Government hascertain rights in this invention.

FIELD

This invention relates generally to the field of radio signal detectionand bearing determination, and more specifically to systems and methodsfor simultaneous radio detection and bearing.

BACKGROUND

The radio spectrum is divided up into bands by frequency andcorresponding wavelength. For example, Extremely Low Frequency (ELF)ranges from 3-30 Hz and Super Low Frequency (SLF) ranges from 30-300 Hz.Ultra Low Frequency (ULF) ranges from 300-3000 Hz, Very Low Frequency(VLF) ranges from 3-30 kHz and Low Frequency (LF) ranges from 30-300kHz. Medium Frequency (MF) ranges from 300-3000 kHz and is common for AMbroadcasts. High Frequency (HF) ranges from 3-30 MHz and is common forshortwave and amateur radio broadcasts. Very High Frequency (VHF) rangesfrom 30-300 MHz and Ultra High Frequency (UHF) ranges from 300-3000 MHzand both are common for television as well as general radiotransmission. Super High Frequency (SHF) ranges from 3-30 GHz andExtremely High Frequency (EHF) ranges from 30-300 GHz, and both areapplicable to microwave devices.

The UHF and VHF frequency ranges in particular are extremely common forhand held radio transmission and reception. Operable over varyingdistance bearings depending on geography and power of the transmitterthese devices permit one or more parties to communicate verbally. Insome situations data transmission may also be performed.

As with normal face to face communication, the duration of atransmission may be extremely short. Often these radios may be usedbetween family or business parties for a wide range of communicationneeds. Further still, these radios may be utilized in search and rescueoperations where the transmitting party has limited or reduced powerand/or may be week from injury and therefore unable to maintain contactfor long. More concerning, these radios are also frequently employed inclandestine operations. The signal to give a command or indicate thearrival of a party or other event may be extremely brief, yet haveprofound consequences.

Indeed whether for defense, the location of a lost party, or otherpurpose, it is often highly desirable to know both when a radiocommunication occurs and from which direction, i.e., bearing, the signalcame.

Several attempts have been made to address the need for a system andmethod capable of signal detection and bearing determination, especiallyfor UHF and VHF signal transmissions. In general these systems andmethods have adopted one of two forms.

In the first case, the system scans a single narrowbandreceiver/demodulator through all possible signal locations in thespectrum. When a signal is detected in the demodulator, the tuner stopsscanning and records the voice channel as well as the signal interceptparameters. The detection receiver sends the intercept frequencyinformation to a second receiver which determines the signal's bearing.

A number of shortcomings are immediately apparent with such a system.First, as there are two receivers, one for detection and one forbearing, a short signal transmission caught by the detection receivermay no longer be in transmission by the time the detection receiverprovides the intercept frequency to the bearing receiver.

In addition, a single receiver scanning the spectrum may well miss shortduration transmissions that occur elsewhere in the spectrum from wherethe scan is currently active. Further still, when stopped to record onetransmission that has been found, additional transmissions that may beoccurring will be missed.

In the second case, the system digitizes samples of the waveform for theentire frequency band of interest. A mathematical operation is thenperformed to measure all the frequencies that may contain signals. As inthe first case, the detection of a signal triggers the activation of asecond receiver for bearing determination.

Again, a number of shortcomings exist. As in the first case systems,bearing determination is a separate and subsequent operation performedby a second receiver. For short transmissions there is a high likelihoodof the bearing determination failing as the signal transmission may wellhave ended. In addition, even for multiple signals, the bearingdetermination occurs on a one by one basis.

Recordings of the detected signal(s) are accomplished by digitallydemodulating to a receiver. Power requirements for digital filtering anddemodulation are quite high, and cooling of the system components isoften also required in warm environments.

Reliant on large components, including the antennas, these systems(first or second case) generally require a good deal of physicalreal-estate and power supply capability in order to operate. Moreover,systems under the first case and the second case are not easilyportable, and typically are quite expensive to install and maintain.

Hence, there is a need for a radio signal detection and bearing systemand method that overcomes one or more of the issues and problemsidentified above.

SUMMARY

This invention provides a simultaneous radio detection and bearingsystem and method.

In particular, and by way of example only, according to one embodimentof the present invention, provided is a simultaneous radio detection andbearing system, an RF conditioning subsystem having a plurality ofarrays of Frequency Range signal receiving channels, the RF conditioningsubsystem operable to combine the signals from the arrays as a firstinternal data stream; a coherent multi-channel digitizer subsystemcoupled to the RF conditioning system, the coherent multi-channeldigitizer subsystem operable to generate a time domain snapshot of thefirst internal data stream; an audio recording subsystem coupled to theRF conditioning subsystem; and a processor coupled to the coherentmulti-channel digitizer subsystem and the audio recording subsystem, theprocessor operable to transform the time domain snapshot to a frequencyspectrum and identify at least one signal above a threshold at adetermined frequency, determine the bearing of the signal, and providethe determined frequency of a selected identified signal to the audiorecording subsystem, the audio subsystem contemporaneously recording theselected signal upon the determined frequency.

Moreover, according to yet another embodiment, of the present invention,provided is a simultaneous radio detection and bearing system, an RFconditioning subsystem having a plurality of First Frequency Range andSecond Frequency Range signal receiving channels, the RF conditioningsubsystem operable to combine First Frequency Range and Second FrequencyRange signals as a first internal data stream; a coherent multi-channeldigitizer subsystem coupled to the RF conditioning system, the coherentmulti-channel digitizer subsystem operable to generate a time domainsnapshot of the first internal data stream; an audio recording subsystemcoupled to the RF conditioning subsystem; and a processor coupled to thecoherent multi-channel digitizer subsystem and the audio recordingsubsystem, the processor operable to transform the time domain snapshotto a frequency spectrum and identify at least one signal above athreshold at a determined frequency, determine the bearing of thesignal, and provide the determined frequency of a selected identifiedsignal to the audio recording subsystem, the audio subsystemcontemporaneously recording the selected signal upon the determinedfrequency.

Further, according to yet another embodiment of the present invention,provided is a simultaneous radio detection and bearing system,including: an RF receiver and block down converter subsystem operable toreceive First Frequency Range and Second Frequency Range signals on atleast four channels and provide a combined intermediate analog frequencysignal; a coherent multi-channel digitizer subsystem coupled to thereceiver and block down converter subsystem, the coherent multi-channeldigitizer subsystem operable to receive the combined intermediate analogfrequency and render a time domain snapshot for the frequency domain; aprocessor coupled to the coherent multi-channel digitizer subsystem, theprocessor operable to transform the time domain snapshot to a frequencyspectrum and identify at least one signal at a determined frequency andcontemporaneously determine the bearing of the signal based on acomparison of signal phase established by the coherent multi-channeldigitizer; and an audio recording subsystem coupled to the receiver andblock down converter subsystem and the processor, the audio subsystemoperable to demodulate and record an audio signal from the analogintermediate frequency signal on the determined frequency provided bythe processor.

In yet another embodiment provided is a method of simultaneous radiodetection and bearing, including: providing an RF receiver andconditioning subsystem having at least four First Frequency Rangechannels and Second Frequency Range channels; sampling the FirstFrequency Range and Second Frequency Range spectrum each in apredetermined range; converting the samples into a first internal datastream; Simultaneously providing the internal signal to a digitizersubsystem and an audio recording subsystem; digitizing the internalsignal at predetermined intervals to provide a time domain snapshot;transforming the time domain snapshot with a FFT to provide a frequencyspectrum; and comparing the frequency spectrum to a threshold toidentify keyed signals; in response to at least one identified keyedsignal, determining the frequency of the signal and the bearing of thesignal about simultaneously, and for a selected identified signal,engaging the audio subsystem to demodulate the internal signal at thedetermined frequency and record the selected identified signal, therecording of the signal being and the determination of bearing beingabout contemporaneously; and outputting the identified signal frequency,bearing and selected signal recording.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a high level overview of a simultaneous radiodetection and bearing system in accordance with at least one embodiment;

FIG. 2 is a perspective view of a simultaneous radio detection andbearing system in accordance with at least one embodiment;

FIG. 3 is a general block diagram of the components providing thesimultaneous radio detection and bearing system in accordance with atleast one embodiment;

FIG. 4 is a refined block diagram of the components providing thesimultaneous radio detection and bearing system in accordance with atleast one embodiment;

FIG. 5 is a flow diagram of a method for radio signal detection andbearing determination in accordance with at least one embodiment;

FIG. 6 is a block diagram of the processor actions in accordance with atleast one embodiment;

FIG. 7 illustrates an general overview of phase interferometry bearingdetermination in accordance with at least on embodiment;

FIG. 8 illustrates an advanced overview of phase interferometry bearingdetermination in accordance with at least on embodiment;

FIG. 9 is an illustration of multiple simultaneous radio detection andbearing systems used cooperatively to determine position; and

FIG. 10 is a block diagram of a computer system providing a processor inaccordance with at least one embodiment.

DETAILED DESCRIPTION

Before proceeding with the detailed description, it is to be appreciatedthat the present teaching is by way of example only, not by limitation.The concepts herein are not limited to use or application with aspecific method of simultaneous radio detection and bearingdetermination. Thus, although the instrumentalities described herein arefor the convenience of explanation, shown and described with respect toexemplary embodiments, it will be appreciated that the principles hereinmay be applied equally in other types of methods involving the detectionof radio signal(s) and determination of bearing(s).

FIG. 1 illustrates an exemplary simultaneous radio detection and bearingsystem (“SRDBS”) 100. As illustrated the SRDBS 100 is deployed in anarea and without the requirement of an established infrastructure, suchas for example, but not limited to a foundation, power grid, supportstaff, etc. . . . In at least one embodiment, SRDBS 100 is operable atlow power and as such may be remotely operated by an independent andsustainable power source, such as but not limited to solar energy, windenergy, fuel cell and combinations thereof.

In at least one embodiment the sustainable power source is a solar array102. In at least one alternative embodiment the sustainable power sourceis wind turbine 104. Moreover, SRDBS 100 is operable in locationsremoved from traditional power sources such as power grids, and/or maybe powered in such a manner so as to not be detectible as a consumingappliance connected to a power grid.

As shown, SRDBS 100 is operable to detect multiple different radiosignals, indicated by dotted lines 106, 108 and 110 concurrentlyemanating from radio R1 (112), radio R2 (114) and radio Rn (116) and foreach detected radio signal, to simultaneously determine the frequency ofthe signal and the bearing of the radio signal. Based on a system ofprioritization, such as for example signal strength and/or priorityfrequency, SRDBS 100 will also record as many detected signals aspossible.

Indeed as shown, radio 112 is physically in a very different locationfrom radio 114. Additional radios, e.g. radio 116, may be in yetdifferent physical locations, close to or even co-located with radio 112or radio 114. Further still, radio 112 may well be a UHF radio whereasradio 114 is a VHF radio. Regardless, SRDBS is operable tosimultaneously detect all transmissions from radios R1˜Rn (112, 114,116). Moreover, it is important to understand that it is not merely thesimultaneous detection of the signals that is advantageously permittedby SRDBS 100, but also the simultaneous determination of bearing andrecording for each selected detected signal.

In addition to the detection of radio signals, SRDBS 100 also determinesbearing to each signal, e.g. bearings 118, 120 and 122 relative to atleast one known reference axis 124 of SRDBS 100. Advantageously, thedetermination of bearing occurs contemporaneously with theidentification of the detected signals. In addition, for each detectedradio signal, SRDBS 100 will capture and record the detected signal.

As used herein, the terms “contemporaneously” and “simultaneously” areunderstood and appreciated to be actions or activities that occur inreal time at about the same instant with respect to a human perspective.Moreover, it is understood and appreciated that differences intransmission line length, processor operation sequencing and or otherfactors may introduce small differences in temporal occurrence such thatthe events are more property described as “near real time.” Accordingly,contemporaneously and simultaneously are understood and appreciated toencompass events that are both real time as well as near real time.

To clarify some general terms, as used herein, signals are understoodand appreciated to be transmissions within a spectrum. A spectrum isunderstood as a range of frequencies. A channel is the end-to-endconfiguration of an antenna to digitizer or audio subsystem provided toreceive signals within a spectrum.

Shown within the dotted section 150 is a conceptual block diagram ofSRDBS 100 in accordance with at least one embodiment. As shown, SRDBS100 is comprised generally of a RF conditioning subsystem 152, amulti-channel digitizer subsystem 154, an audio recording subsystem 156and a processor 158. More specifically, RF signals are received by theRF conditioning subsystem 152 and provided simultaneously to themulti-channel digitizer subsystem 154 and the audio recording subsystem156, each in respective communication and control with the processor158. Though each component has been illustrated for simplicity as asingle unit, it is understood and appreciated that each subsystem maywell include multiple internal systems/subsystems. Further, in varyingembodiments the multi-channel digitizer subsystem 154 may include aprocessor as well.

As discussed below, in at least one embodiment the processor 158 isprovided in the form of a general computer such as a laptop. In at leastone embodiment, by the execution of computer program instructionsdirecting the operation of the processor, SRDBS 100 simultaneouslydetects one or more radio signals, and for each detected radio signaldetermines the bearing and captures an audio recording of the detectedsignal.

In at least one embodiment, each detected signal, 106, 108 110, itsrespective bearing, 118, 120, 122, and recording is provided to a userwho is present with SRDBS 100. In at least one other embodiment, eachdetected signal, 106, 108 110, its respective bearing, 118, 120, 122,and recording is transmitted to a user at an operation base 126. Invarying alternative embodiments, SRDBS 100 may also warehouse theinformation locally or only locally warehouse the information for laterretrieval, and therefore remain substantially stealth in operation.

FIG. 2 is an enlarged perspective view of SRDBS 100. As shown, SRDBS 100has a plurality of arrays of Frequency Range signal receiving channels.More specifically, as shown, in at least one embodiment SRDBS 100 hastwo sets of antenna arrays: First Frequency Range array 200 are theouter four antennas, A₀, A₁, A₂ and A₃ and Second Frequency Range array202 are the inner four antennas a₀, a₁, a₂ and a₃. The antenna arraysare arranged as concentric squares, and as shown for at least oneembodiment, the inner arrangement of Second Frequency Range array 202 isforty five degrees off rotation from the outer arrangement of FirstFrequency Range array 200. With respect to the above definition of“channel” it is therefore clear that SRDBS 100 has a plurality of FirstFrequency Range and Second Frequency Range channels, and morespecifically for the embodiment shown in FIG. 2, four First FrequencyRange and four Second Frequency Range channels. As is further discussedbelow, the configuration as an array permits the detection of phase.

In at least one embodiment, the First Frequency Range is the VHF rangeand the Second Frequency Range is the UHF frequency range. In at leastone alternative embodiment, the First Frequency Range is the LF and/orMF range. Further still in yet another embodiment the Second FrequencyRange is the SHF and/or EHF range. Moreover, in varying embodiments theFirst Frequency Range and the Second Frequency Range are different andeach is selected from the group consisting of LF, MF, HF, VHF, UHF, SHF,EHF and combinations thereof. Still further, although SRDVS 100 is shownand described with respect to figures as having two sets of arrays, invarying alternative embodiments SRDBS 100 may have at least oneadditional array of Third Frequency Range signal receiving channels.

For ease of illustration and discussion, the examples herein describedand depicted relate to detection of UHF and VHF signals as may becommonly provided by hand held radios, however it is understood andappreciated that the descriptions, system and methodologies are equallyapplicable to embodiments of SRDBS 100 configured for detection of otherfrequency ranges and a plurality of different frequency rangespotentially including but not limited to UHF and VHF. Moreover, in atleast one embodiment the First Frequency Range is VHF and the SecondFrequency Range is UHF.

In at least one embodiment SRDBS 100 is substantially square, having aside dimension 204 of about twenty inches (20″), and a height dimension206 of about five inches (5″). The VHF antennas are about six inches(6″) tall and the UHF antennas are about four inches (4″) tall.Moreover, RDVS 100 is relatively small, as compared to other devicesincorporating typical VHF antennas of about forty two inches (42″), andUHF antennas of thirteen inches (13″). Further, in at least onembodiment, SRDBS 100 incorporates visual camouflage as suggested bypatch 208.

SRDBS 100 is operable to detect a plurality of substantially concurrentradio transmissions, of which transmission 210 from radio 212 isexemplary. Further still, having at least one pre-established referenceaxis 124 SRDBS 100 is operable to determine the bearing 214 of eachdetected transmission 210 simultaneously with respect to the referenceaxis.

In at least one embodiment, SRDBS 100 further includes an optional GPSand electronic compass subsystem so as to accurately and independentlydetermine the pre-established SRDBS position and reference axis 124. Invarying embodiments, SRDBS 100 may also be deployed upon a vehicle, suchas but not limited to a car, truck, train, boat, or aircraft. Moreover,SRDBS 100 is generally a portable device requiring little or no areapreparation prior to installation, and easily deployed by one or a fewpersonnel. Indeed, in at least one embodiment, SRDBS 100 is humanportable. As compared to a traditional ground or ship based installationfor radio detection, embodiments of SRDBS 100 may be considered asdisposable, having minimal infrastructure and/or production costs.

FIG. 3 conceptually illustrates the general arrangement andinterconnection of SRDBS 100 components. More specifically the RFconditioning subsystem 152 has a plurality of UHF and VHF channels, ofwhich UHF channel 300 and VFH channel 302 are exemplary. In at least oneembodiment, there are four UHF channels 300 and four VHF channels 302.

The RF conditioning subsystem 152 is operable to combine the UHF and VHFspectrums as a first internal data stream 304 (A₀a₀, A₁a₁, A₂a₂, A₃a₃).In varying embodiments the first internal data 304 may be an analogintermediate frequency or a digital signal. As such, as used herein theterms “data stream” are understood and appreciated to apply toinformation that is transferred internally, regardless of whether it isas an analog signal or digital signal or other form of transmission.

Moreover, in at least one embodiment, each channel of the RFconditioning subsystem 152 is a digital receiver and filter, the firstinternal data stream 304 therefore being a digital signal. In at leastone alternative embodiment, each channel of the RF conditioningsubsystem 152 is an analog receiver and block down converter, the firstinternal data stream 304 being an analog intermediate frequency signal.

Each first internal data stream 304 is contemporaneously provided to themulti-channel digitizer subsystem 154 and the audio recording subsystem156. Indeed, as each first internal data stream 304 is simply divided,in at least one embodiment the delivery of the first internal datastream 154 to the multi-channel digitizer subsystem 154 and the audiorecording subsystem 156 is simultaneous.

Indeed, because the same first internal data stream 304 is provided tothe multi-channel digitizer 154 and the audio recording subsystem 156,the same information used to identify a transmitted signal is also usedto record that transmitted signal. This is accomplished without the useof an additional receiver. It is understood and appreciated that due tothe operations performed to detect a signal and determine it'sfrequency, an element of delay does exist between the determination andengagement of the audio recording subsystem 156. However for practicalpurposes this delay is so small as to be insignificant for real worldpurposes. Moreover in at least one embodiment, SRDBS 100 is operable tosample the spectrum with sufficient speed so that detection, frequencymeasurement, and command of the audio recording subsystem 156 to startsignal capture all occur within a time frame of less than about 0.1second. This is substantially near-real-time as discussed above and istherefore for at least one embodiment considered to be a simultaneousaction. As such, for at least one embodiment, the loss of any part ofthe transmission is generally accepted to be insignificant to theinterpretation of the recorded signal. In at least one alternativeembodiment, a buffer is employed to delay the signal as provided to theaudio recording subsystem 147 with a signal appropriately delayed so asto account for the operations for detection and determination.

The multi-channel digitizer subsystem 154 is a coherent multi-channeldigitizer. In at least one embodiment four digitizers are made coherentby using a common reference sampling clock, and collectively providecoherent multi-channel digitizer 154. For conservation of space, powerand other resources, in at least one embodiment the coherentmulti-channel digitizer 154 is provided by two coherent dual channeldigitizers, of which coherent dual channel digitizer 306 is exemplary.Moreover, each of the digitizers 306 is connected to a single referenceoscillator so as to yield coherent output data streams. Each of the fourinternal data streams 304 is coupled to one of the four digitizers,e.g., two internal data streams 304 to each dual channel digitizer 306.

The multi-channel digitizer subsystem 154 is operable to receive thefirst internal data stream 304 from the RF conditioning subsystem 152and generate a time domain snapshot of the first internal data stream304. The time domain snapshot is provided to the processor 158.Advantageously, in providing the time domain snapshot, the phase of eachchannel is retained from the first internal data stream 304 by thecoherency of the dual channel digitizers 306. More specifically, as isfurther set forth below, because the down converters of the UHF channels300 and VHF channels 302 use a common clock, the relative phase ispreserved between channels at each frequency output of the FourierTransform performed to transform the time domain snapshots into afrequency spectrum.

The processor 158 is operable to transform the time domain snapshotprovided by the multi-channel digitizer subsystem 154 into a frequencyspectrum. In at least one embodiment this transformation is performed byapplying a Fast Fourier Transform (FFT) to the time domain snapshot. Inat least one embodiment the FFT is provided as a fast computation of theDiscrete Fourier Transform (DFT) implemented by the processor, orgeneral computer providing the processer as discussed below. In at leastone alternative embodiment the FFT is provided by a hardware DigitalSignal Processor (DSP) specifically optimized for the SRDBS 100. Morespecifically, in at least one embodiment the DSP is incorporated as partof the multi-channel digitizer subsystem 154, such that the muti-channeldigitizer subsystem 154 receives the first internal data stream 304 fromthe RF conditioning subsystem 152, generates a time domain snapshot andtransforms the snapshot into a frequency spectrum.

It is understood and appreciated that signal transmissions may take avariety of forms, such as for example voice transmission via push totalk radios, pulse transmissions and burst transmissions. Whereas avoice transmission is generally of a relatively long duration—tens ofseconds or more, pulse and burst are characterized by short durations,pulse and burst transmissions being generally any transmission thatcombines a very high data signaling rate with a very short transmissiontime.

In at least one embodiment where SRDBS 100 is to be deployed for thedetection of hand radios, the use of a sample rate that is faster thanthe statistical key time (e.g. the talk time) alleviates the need forsome embodiments of SRDBS 100 to utilize buffers so as to process all ofthe data provided by the first internal data stream 304. For at leastone such embodiment, a sample of about a tenth of a millisecond per timedomain snapshot has been found sufficient to identify hand radio signalsand cue the audio recording subsystem 156. Partial sampling alsoadvantageously permits lower power consumption by the processor or DSPas well as reducing cooling requirements.

In alternative embodiments, such as where pulse transmissions, bursttransmissions, and/or other short duration transmissions are desiredtargets for detection, various embodiments of SRDBS 100 employ ping pongbuffers, e.g. double buffers. While one buffer is being processed, theother buffer is being loaded—switching between the two permits all datato be processed without loss or data pileup. In general, the use of pingpong buffers increases the system complexity of SRBDS 100 and powerconsumption as more data processing and manipulation is being performed.As such, unless the end use so requires, embodiments of SRBDS 100 may besimplified by using a partial sampling of each time domain snapshot asdescribed with respect to hand radio transmissions.

As is further discussed below a threshold, such as an amplitudethreshold, is applied to the frequency spectrum such that signals thatbreach the threshold are taken as identified signal transmissions. Foreach identified signal, the frequency is determined, the bearing iscalculated and, for at least a subset of the detected signals, thefrequency of a selected number of the detected signals is provided tothe audio recording subsystem 156.

In at least one embodiment, the audio recording subsystem 156 includes aplurality of FM radios, of which radio 308 is exemplary. Each radio 308has a local oscillator 310, FM demodulator 312 and an audio recorder314. Although there is a one-to-one relationship between each RFconditioning subsystem 154, each first internal data stream 304 and eachdigitizer, SRDBS 100 provides a plurality of radios 308. Moreover, asdiscussed above there are four channels, operable to detect N concurrentsignals simultaneously.

To effectively record each and every of the N detected signals, SRDBS100 would ideally provide N radios 308. However, in at least oneembodiment SRDBS 100 provides less than N possible radios 308, e.g.SRDBS 100 provides M radios 308 where M is less than a maximum N.Clearly, in many situations M radios will be sufficient as the detectednumber of signals N may well be less than M. Where N is indeed greaterthan M, a prioritization scheme is employed to select detected signalsfor recording.

Of the detected signals, a selected number are recorded. Initially thenumber of simultaneous recordings is at least that of the number ofradios 308 provided. When the number of detected signals is greater thanthe number of radios 308 provided, at least one selection process isapplied, such as for example the selection of detected signals havingthe greatest transmission power, correlation to a priory frequencyand/or combinations thereof as well as other methodologies.

When a frequency is provided by the processor 158 to an FM radio 308,the local oscillator 308 tunes to the specified frequency and the firstinternal data stream 304 is demodulated to the detected signal. Asshown, in at least one embodiment the interconnections between themulti-channel digitizer 154, the processor 158 and the audio recordingsubsystem 156 is accomplished with USB interface protocols 316.

As shown and described, in at least one embodiment there are at leastfour internal data streams 304, one from each set of channels. In atleast one embodiment, a single channel is selected and hardwired to theaudio recording subsystem 156. Such an embodiment simplifies design andfabrication. An appropriate number of splitters and/or amplifiers areutilized to distribute the single hardwired channel to each of theradios provided 308.

In at least one alternative embodiment, the plurality of internal datastreams 304 are combined so as to provide fault tolerance and improvesignal to noise ratios. Moreover, in at least one embodiment anoptimally weighted sum of all four channels is employed and provided tothe audio recording subsystem 156.

As the detection process as performed by SRDBS 100 is a continuouslyrepeating process, in at least one embodiment the repeating cycles areused to cue when a recording should end. More specifically if a signalis not detected in a consecutive number of snapshots, the audiorecording subsystem 156 will be disengaged for that previouslyidentified signal. Specifically, in at least one embodiment the numberof consecutive snapshots with an absent signal to trigger the end of arecording is three (3).

Similarly, in at least one embodiment a recording is cued to end if thesignal has continued beyond a user defined duration. Moreover, asindicated above various embodiments of SRDBS 100 may have a varyingnumber M of radios 308, however it is understood and appreciated thatthe number of detected signals N may in some cases be greater than thenumber of available radios M. Various different prioritization schemesmay be employed for different configurations, such as, but not limitedto: predetermined frequencies of priority, signal power, bearing, andother factors as may be desired by an end user of SRDBS 100.

As the audio recording subsystem 156 receives the same first internaldata stream 304 as is provided to the multi-channel digitizer subsystem154, the audio recorder 314 then records the transmission in about realtime in an appropriate format, such as for example, *.wav, * mp3, *.vox,*.ra, or other free or proprietary audio file format. In at least onealternative embodiment, the signal is recorded in a pre-detected(un-demodulated) format (such as the intermediate frequency or digitalsignal comprising the first internal data stream 304).

Moreover, with respect to SRDBS 100 as conceptually shown in FIG. 3, itis understood and appreciated that because the same first internal datastream 304 is being provided to both the multi-channel digitizersubsystem 154 and the audio recording subsystem 156, the sameinformation being used to identify the transmitted signal is used torecord the transmitted signal. Moreover a second receiver is notrequired to tune to the identified frequency with the hope of findingand then recording the transmitted signal. Use of the same firstinternal data stream 304 for both operations advantageously minimizesthe chance of missing the recording of an identified signal

FIG. 4 is a more refined system block diagram of SRDBS 100 furtherillustrating for at least one embodiment, the components of the RFconditioner subsystem 152, the multi-channel digitizer subsystem 154,the audio recording subsystem 156 and processor 158.

More specifically, within RF conditioner subsystem 152, for at least oneembodiment there are four UHF signal conditioners, of which UHF signalconditioner 400 is exemplary. An antenna 402 is coupled to a low noiseamplifier 404 which in turn is coupled to a filter 406 set for thefrequency range of about 462 MHz˜467 MHz. The output from filter 406 isdirected through pre-amplifier 408.

So as to provide a first internal data stream 304 as an intermediatefrequency, a heterodyne process is applied. Stated generally, a firstlocal oscillator 410 set to about 418 MHz provides a predeterminedsignal to each UHF signal conditioner. Moreover, in at least oneembodiment first oscillator 410 is a 418 MHz crystal oscillator. In atleast one embodiment the same first oscillator 410 is used to providethe same predetermined signal to each of the respective UHF signalconditioners.

With respect to UHF signal conditioner 400, this predetermined signal isprovided to mixer 412 where it is combined with the output frompre-amplifier 408. As the heterodyne process provides two newfrequencies the output from mixer 412 is directed through band passfilter 414 set for the frequency range of about 44 Mhz˜49 MHz so as toprovide only the desired spectrum, and then subsequently passed tointermediate frequency amplifier 416.

The VHF array is composed of active antennas 422. The use of the activeantenna unit in at least one embodiment is highly advantageous for manyreasons. The use of active antennas 422 permits antenna height of aboutsix inches (6″). There is also no transmission line as is typical with anormal VHF antenna. The active antenna unit 424 is specificallypre-designed to have an input matched to about the same impedance of theactive antenna 422, thereby insuring that the active antenna unit 424receives a substantial fraction of the antenna energy.

Similarly, within RF conditioner subsystem 152, for at least oneembodiment there are four VHF signal conditioners, of which VHF signalconditioner 420 is exemplary. An antenna 422 is coupled to an activeantenna unit 424 which in turn is coupled to a filter 426 set for thefrequency range of about 138 MHz˜174 MHz so as to provide only thedesired spectrum. The output from filter 426 is directed throughpre-amplifier 428.

A second local oscillator 430 set to about 133 MHz provides apredetermined signal to each VHF signal conditioner. Moreover, in atleast one embodiment second oscillator 430 is a 133 MHz crystaloscillator. In addition, in at least one embodiment the same secondoscillator 430 is used to provide the same predetermined signal to eachof the respective UHF signal conditioners.

With respect to VHF signal conditioner 420, this predetermined signal isprovided to mixer 432 where it is combined with the output frompre-amplifier 428. As this heterodyne process provides two newfrequencies the output from mixer 432 is directed through band passfilter 434 set for the frequency bearing of about 5 Mhz˜41 MHz so as toprovide only the desired frequency, and then subsequently passed tointermediate frequency amplifier 436.

The first internal data stream, e.g., the intermediate frequencyprovided by each channel set of a UHF signal conditioner and a VHFsignal conditioner is then combined and provided to one channel of themulti-channel digitizer 154, of which coherent multi channel digitizer440 is exemplary. As noted above, the intermediate frequency iscontemporaneously provided to the audio recording subsystem 156 of whichFM radio 308 is exemplary.

As noted above, in at least one alternative embodiment, the RFconditioner 152 has a plurality of digital UHF receivers each pairedwith an appropriate digital bandpass filter and a plurality of digitalVHF receivers each pared with an appropriate digital bandpass filter.The digital configuration effectively eliminates the use of a downconverter within the RF conditioner 152. In at least one embodiment,this elimination provides a number of advantages to a SRDBS 100, such asbut not limited to being smaller, less complex, requiring lessoperational power, a greater tolerance for temperature fluctuation, andcombinations thereof. The output from the respective digital receiversand filters is combined as the first internal data stream 304

In varying embodiments the ADC 442 has a clock frequency in a range ofabout 90 MHz˜1 GHz and a resolution selected within a range of about 6to about 64 bits. In at least one embodiment, coherent multi channeldigitizer 440 is an analog to digital converter (ADC) 442 receiving theintermediate frequency and converting the continuous signal to discretedigital numbers. In general, the four ADCs 442 are matched in kind andselected from the group consisting of direct conversion ADCs,successive-approximation ADCs, ramp-compare ADCs, Wilkinson ADCs,integrating ADCs, delta-encoded ADCs, pipeline ADCs, Sigma-Delta ADCs,Time-interleaved ADCs, and ADC with intermediate FM stage. Moreover, theselection of the ADCs 442 is an optimal selection based upon thecombination of clock frequency and bit rate to maximize the dynamicrange of the snapshot, alias error correction, and/or other factorsrelevant for the intended environment in which SRDBS 100 is to be used.

In data sampling systems, it is important to provide samples of enoughdata to effectively provide all of the necessary data for the type ofdesired processing and evaluation. In at least one embodiment, thesignals being sampled are about 12 kHz wide and distributed across abandwidth of about 36 VHF MHz and bandwidth of about 6 UHF MHz for atotal of about 42 MHz of bandwidth of interest. For such an embodiment,a sampling rate of about 2.38 times the bandwidth of interest providesadequate sampling. Although higher sampling rates may be selected, andor appropriate for alternative embodiments, greater sampling ratestypically also require greater power supply for the system.

In addition, in at least some embodiments the aliasing property of thedigitizer may advantageously be exploited. More specifically, for adigitizer running at 100 MHz the SRDBS 100 will unambiguously detectfrequencies from 0 to 50 HMz. If a signal comes in at 75 HMz it is notlost, but rather it maps back, i.e. aliases, as 25 HMz. Depending on enddeployment and use desires such aliasing may or may not be desired,however for situations such as the detection of hand radios, thisbehavior once again provides advantageous power savings, design andfabrication simplicity to at least one embodiment of SRDBS 100.

In at least one embodiment, each ADC 442 has a clock frequency of 100MHz and a resolution of 8-bits. Having a clock frequency of 100 MHz,each ADC 442 produces about 16,384 samples, e.g., snapshots,approximately four times per second. As all ADCs 442 are sampled using acommon reference, the time domain snapshots provided by each aresynchronized. For this specific embodiment, the sample rate of 100 MHz,combined with the snapshot width of 16,384 samples yields a frequencyresolution of approximately 6.1 kHz per frequency cell as results fromthe FFT. This is approximately half the closest channel spacing ofhandheld radios used in these applications, providing a high probabilityof simultaneously detecting adjacent signal channels. The 8 bitdigitizer, combined with the processing gain of a 16,384 sample snapshotproduces a digital dynamic range of approximately 84 dB, more thanadequate for spurious signal elimination in the anticipated signalenvironment.

With respect to FIG. 4, each FM radio 308 includes a tunable oscillator450, such as a tunable crystal oscillator, that is responsive to afrequency provided by the processor 158. The tuned frequency signal fromthe oscillator 450 is provided to mixer 452 which also receives thefirst internal data stream 304, e.g., the intermediate frequency signalor the digital signal. Output from the mixer is provided to thedemodulator 454 that extracts the audio signal from the intermediatefrequency and provides the audio signal to the audio recorder 456. It isunderstood and appreciated that as an intermediate frequency is in use,an offset for the local oscillator may be appropriate. The specific typeand/or amount of offset is of course determined by the type of signalbeing detected. For example, for a typical FM signal, in at least oneembodiment utilizing a 455 kHz discriminator, subtracting 455,000 fromthe detected frequency before commanding the local oscillator frequencyis appropriate. If the signal is of a single sideband modulation, anoffset by either positive or negative half bandwidth is appropriate.Moreover, it is understood and appreciated by those skilled in the artthat appropriate offsets commensurate with specific demodulators areapplied based on the user determined types of signals that variousembodiments of SRDBS 100 are intended to detect.

So as to facilitate ease of connection and low power usage throughoutthe SRDBS 100, in at least one embodiment, the interconnections betweenthe processor 158, the multi-channel digitizer subsystem 154 and theaudio recording subsystem 156 are USB protocols 316.

The processor 158 is operable to transform the time domain snapshotprovided by the multi-channel digitizer subsystem 154 to a frequencyspectrum and identify at least one signal above a threshold at adetermined frequency. For each signal detected above the establishedthreshold, the bearing of the signal is determined and the frequency isprovided to the audio recording subsystem 156 so that a contemporaneousrecording of the signal can be obtained.

FIGS. 5 and 6 conceptually illustrate the method 500 for detecting aradio signal and bearing. More specifically, FIG. 5 presents a highlevel flow diagram that in connection with FIGS. 1-3 and 5 presents amethod for at least one embodiment of detecting a radio signal andbearing. It will be appreciated that the described method need not beperformed in the order herein described, but that this description ismerely exemplary of at least one preferred method of detecting a radiosignal and bearing.

As shown in FIG. 5 the method typically commences with SRDBS 100 beinginitialized for signal detection, block 502. In general, initializationmay include such activities as deploying SRDBS 100 in a desired areaand/or powering up SRDBS 100. Once initialized, SRDBS 100 commencescollecting time domain snapshots of UHF and VHF environments. Asdescribed above, in at least one embodiment SRDBS 100 advantageouslyutilizes four UHF channels and four VHF channels, block 504. Inaddition, it is understood and appreciated that SRDBS 100 is notselectively tuning through each frequency within a desired spectrum,rather SRDBS 100 is sampling an entire frequency spectrum continuously.

Received signals are then converted to a first internal data stream,block 506. In at least one embodiment this first internal data stream isan analog intermediate frequency (IF) as discussed above. In at leastone alternative embodiment, this first internal data stream is a digitalsignal.

As in block 508, the multi-channel digitizer subsystem 154 (see FIGS.2-4) digitizes the first internal data stream to provide a time domainsnapshot 600, see FIG. 6. As in block 510, the processor is operable toreceive the time domain snapshot 600 and apply a FFT 602 to provide afrequency spectrum 604. As is conceptually illustrated in FIG. 6, athreshold 606, e.g. an amplitude threshold, is defined and imposed uponthe frequency spectrum 604, block 512. Signal peaks that breach thethreshold 606 are taken as unknown but determined keyed signals 608whereas those below threshold are taken as general noise.

In at least one embodiment, the threshold is adjustable, therebypermitting fine-tuning to adjust to the desired application of SRDBS100. Moreover, in some embodiment applications it may be desirable toestablish a low threshold so as to ensure a greater likelihood ofidentifying any signal transmissions, even though a lower threshold mayinclude an occasional false identification of noise as a signal. Inother embodiment applications it may be desirable to establish a highthreshold so as to eliminate low level signals which are not of concern.In at least one embodiment the threshold is self tuned by the SRDBS 100employing various methodologies to adaptively respond to the environmentin which SRDBS 100 is deployed.

More specifically, for each frequency spectrum 604, a first frequency isdetermined and selected, block 512. In one embodiment this firstfrequency is at about the lower bound of the spectrum. In at least oneother embodiment this first frequency is at about the upper bound of thespectrum. In yet another embodiment this first frequency is apre-determined highest priority frequency.

The selected frequency is then compared to the threshold, decision 514.If the selected frequency is above the threshold—a determined keyedsignal—the frequency is noted, block 516. If the last frequency in thespectrum has not been reached, decision 518, the next frequency isselected, block 520.

In the event that a keyed signal has been identified, the frequency isnoted, block 516 and the bearing to the keyed signal is determined, 522.The noted frequency is provided to the audio recording subsystem 156. Asthere may be more detected signals then radios available to demodulateand record the signal, a check is performed to query for availableradios, decision 524. If a radio is available, the frequency is providedto the available radio, which in turn tunes to the frequency, block 526.The radio then demodulates the first internal data stream, block 528,and records the signal, block 530.

In the event that no radios are available a test is performed todetermined whether the noted frequency is a selected priority, decision532. In a first example, the selection for priority is determined bysignal strength, such that signals 610, 614 and 612 are classified aspriorities. In a second example, pre-determined frequencies, such assignals 616, 618 and 620 are classified as priorities. In at least oneembodiment, past frequency of use may also be a factor in determiningpriority for recording.

If the determination is yes, a lesser priority recording is preempted asa radio is directed to tune to the noted frequency, block 526. If thefrequency is determined not to be a priority, no recording is made. Whena selected recording is made, this recording is output with the notedfrequency and determined bearing, block 534. The recording willgenerally continue until preempted by a higher priority signal, or untilit is found to be absent in a series of consecutive time domainsnapshots.

Moreover, as SRDBS 100 cycles through time domain snapshots, previouslyidentified radio transmissions will again be re-identified. A flagsystem may be used to track previously identified signals, and, in atleast one instance trigger a notification if the bearing of the signalchanges. Further, the flag may be used to maintain the operation of theradio in the audio recording subsystem 156 for the duration of thedetected signal. As noted above there are 1 to M radios and in someinstances there may be more than M signals detected. By using flags witha range of priorities the audio subsystem 156 can easily be directed asto which signals to record.

In at least one embodiment this output information is transmitted to areceiving location, e.g. base 126 or a local user. In at least onealternative embodiment, this output information is written to a localstorage device, such as a hard drive. If SRDBS 100 is to continuecollecting time domain snapshots, decision 538, the process returns toblock 504. If not, SRDBS 100 ceases collecting time domain snapshots.

As suggested by the heavy parallel lines 536, the process of determininga frequency as a keyed frequency, determining the bearing and recordingthe frequency if radios are available or when it is a selected priorityare actions that are performed substantially simultaneously. Further, itis important to note that the detection of radio signals and bearing isa continual process. Regardless of whether a signal has been detected ornot (and accordingly it's frequency noted and bearing determined) themethod 500 returns to block 504.

The determination of bearing is based in at least one embodiment onphase interferometry. FIG. 7 is a top view of SRDBS 100 according to atleast one embodiment, the VHF array antennas 700 are the outer fourantennas, A₀, A₁, A₂ and A₃. The UHF array antennas 702 are the innerfour antennas a₀, a₁, a₂ and a₃. Moreover, the antennas are arranged asconcentric squares. Moreover the physics and the algorithms forprocessing are independent from frequency. For the purposes of thisexample for bearing determination the signal in question is beingreceived by the VHF array antennas 700.

The VHF antennas 700 are spaced a distance d apart as shown by dimensionindicators 704. The incoming signal 706 from the remote radio 708 thathas been detected is incident to SRDBS 100 at angle B. The phase of thesignal 706 a propagated wave front is illustrated by dotted line 710. Inthis example the cycle of the propagated wave front runs from a firstzero value 712 to a Right offset 714, to a second zero value 716, to aLeft offset 718 and finally a third zero value 720. The phase is thefraction of a complete cycle corresponding to an offset in thedisplacement from a specified reference point at time T₀. Moreover, atT₀ the phase 710 of the signal 706 as received by antenna A₀ is 0. Asshown, at T₁, the phase 710 of the signal 706 as received by antenna A₁is greater than zero. Therefore, there is a phase difference, Δβ,between the two VHF antennas A₀ and A₁. The angle B can be calculatedbased on this Δβ, by application of the formula indicated by Equation 1below.

$\begin{matrix}{B = {\sin^{- 1}( \frac{\lambda\Delta\phi}{2\pi\; d} )}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

In Equation 1, B is the bearing in radians. Lambda is the free spacepropagation wavelength at the frequency of interest, e.g., λ=C/f where Cis the speed of light, and f is the frequency. The distance betweenantennas, d, is understood to be in the same units as lambda.

Generally of course the distance d is half the wavelength or less. Toaccount for the possibility of mutual coupling between antennas,calibration of the SRDBS 100 is performed prior to field deployment.

As is clear from the above description and the accompanying figures,there are four VHF and four UHF channels in at least one embodiment ofthe SRDBS 100. The determination of bearing is generally enhanced whenthe incidence of the signal is transverse to the baseline established bytwo antennas. With four antennas for UHF and four antennas for VHF,there are at least two baselines for each. As such, varying embodimentsof SRDBS 100 provide for advantageously enhanced bearing determination.

FIG. 8 illustrates an enhanced bearing determination according to atleast one embodiment. Moreover, as in FIG. 7, FIG. 8 is a top view ofSRDBS 100 according to at least one embodiment, the VHF array antennas800 are the outer four antennas, A₀, A_(b) A₂ and A₃. The UHF arrayantennas 802 are the inner four antennas a₀, a₁, a₂ and a₃. Moreover,the antennas are arranged as concentric squares. For the purposes ofthis first example for bearing determination, the signal in question isbeing received by the VHF array antennas 800.

The VHF antennas 800 are spaced a distance d apart as shown by dimensionindicators 804. The incoming signal 506 from the remote radio 508 thathas been detected is incident to SRDBS 100 at angle B. The phase of thesignal 806 is illustrated by dotted line 810, the phase being thefraction of a complete cycle corresponding to an offset in thedisplacement from a specified reference point at time T₀. Moreover, atT₀ the phase 810 of the signal 806 as received by antenna A₀ is Θ₀. Asshown, at T₁, the phase 810 of the signal 806 as received by antenna A₁is greater than zero. At T₂, the phase 810 of the signal 860 as receivedby antenna A₃ is also greater than zero and greater than signal receivedby antenna A₁. At T₃, the phase 810 of the signal 806 as received byantenna A₂ is greater than zero, but also less than that received byantennas A₁ or A₃.

Indeed in the present example of FIG. 6 there are three different phasesΦ₁, Φ₂ and Φ₃ as received by the different antennas A₁, A₂ and A₃ incomparison to Φ₀ as received by antenna A₀. With the use of fourantennas, the likelihood of some mutual coupling may increase. However,this is advantageously offset by pre-deployment calibration of SRDBS100. It is understood and appreciated that the choice of which antennashould be antenna A₀ and which antennas are therefore antennas A₁, A₂and A₃ is inconsequential. Regardless of how the array is identified,the determined bearing will be the same. It is important to note howeverthat for low amplitude signals, many if not all of the phases may berelatively poor. So as to advantageously resolve this as well as improveoverall identification and performance SRDBS 100 is calibrated beforebeing deployed in real world environment.

In calibrating SRDBS 100, a signal is sent from all known bearing (e.g.,360 degrees) and the relative phases θ₁, θ₂, and θ₃ are measured andrecorded. An unknown signal produces relative phases Φ₁, Φ₂ and Φ₃. Tofind the bearing of an unknown signal, it is basically an iterativeprocess to find the calibration set {θ₁, θ₂, and θ₃} that best “matches”the unknown signal {Φ₁, Φ₂ and Φ₃}. Due to signal noise and systemerrors it is highly unlikely that a perfect match will be found. This isunderstood and therefore a solution is defined to be the best matchfunction G, shown as Equation 2G=cos(θ₁)cos(φ₁)+sin(θ₁)sin(φ₁)+cos(θ₂)cos(φ₂)+sin(θ₂)sin(φ₂)+cos(θ₃)cos(φ₃)+sin(θ₃)sin(φ₃)  Equation2

Moreover the process measures the phase {Φ₁, Φ₂ and Φ₃} for each unknownsignal and then searches through all possible calibration B's and theirassociated phase sets {θ₁, θ₂, and θ₃}, computing G for each one. In thecase of an exact match wherein each F perfectly matches each θ, G willbe three (3). The highest G indicates the best guess at the unknownsignal's bearing. Classically this is known as a Maximum Likelihoodsolution.

In at least one embodiment, multiple SRDBS 100 units are deployed in thesame environment, such as SRDBS 100A and SRDBS 100B shown in FIG. 9.Each is operable as described above. Moreover, SRDBS 100A detects radio900 by receiving radio signal 902A and SRDBS 100B detects radio 900 byreceiving radio signal 902B. Similarly SRDBS 100A detects radio 904 byreceiving radio signal 906A and SRDBS 100B detects radio 904 byreceiving radio signal 906B. SRDBS 100A determines the bearing 908 toradio 900, and likewise SRDBS 100B determines the bearing 910 to radio900. SRDBS 100A determines the bearing 912 to radio 904, and likewiseSRDBS 100B determines the bearing 914 to radio 904.

With a plurality of bearings determined to radios 900 and 904, SRDBS100A and SRDBS 100B in cooperation with one another permit not only thesimultaneous detection of radios 900 and 904 and their respectivebearing, but also through triangulation the actual position of radios900 and 904 based on the known positions of SRDBS 100A and SRDBS 100B.The use of additional SRDBS 100 units permits greater accuracy in thedetermined locations.

The processor 158 of SRDBS 100 is in at least one embodiment aspecialized processor with memory, storage devices and input and outputdevices specifically dedicated to the signal detection and bearingdetermination as described above. For ease in manufacturing, upgrade andflexibility, in at least one embodiment the processor 158 is the centralprocessing unit (CPU) of a general purpose computer, such as a laptop.

With respect to the above description of SRDBS 100 and method 500, it isunderstood and appreciated that the method may be rendered in a varietyof different forms of code and instruction as may be preferred fordifferent computer systems and environments. To expand upon the initialsuggestion of a computer implementation suggested above, FIG. 10 is ahigh level block diagram of an exemplary computer system 1000. Computersystem 1000 has a case 1002, enclosing a main board 1004. The main boardhas a system bus 1006, connection ports 1008, a processing unit, such asCentral Processing Unit (CPU) 1010 and a memory storage device, such asmain memory 1012, hard drive 1014 and CD/DVD ROM drive 1016.

Memory bus 1018 couples main memory 1012 to CPU 1010. A system bus 1006couples hard drive 1014, CD/DVD ROM drive 1016 and connection ports 1008to CPU 1010. Multiple input devices may be provided, such as for examplea mouse 1020 and keyboard 1022. Multiple output devices may also beprovided, such as for example a video monitor 1024, audio system 1026and a printer (not shown).

Computer system 1000 may be a commercially available system, such as adesktop, or for field applications perhaps more appropriately a laptopor even PDA unit provided by IBM, Dell Computers, Gateway, Apple, SunMicro Systems, or other computer system provider. Computer system 1000may also be a networked computer system, wherein memory storagecomponents such as hard drive 1014, additional CPUs 1010 and outputdevices such as printers are provided by physically separate computersystems commonly connected together in the network. Those skilled in theart will understand and appreciate that physical composition ofcomponents and component interconnections comprising computer system1000, and select a computer system 1000 suitable for the schedules to beestablished and maintained.

When computer system 1000 is activated, preferably an operating system1028 will load into main memory 1012 as part of the boot strap startupsequence and ready the computer system 1000 for operation. At thesimplest level, and in the most general sense, the tasks of an operatingsystem fall into specific categories—process management, devicemanagement (including application and user interface management) andmemory management.

In such a computer system 1000, the CPU 1010 is operable to perform oneor more of the tasks associated with the method of simultaneous radiodetection and bearing determination methods as described above. Thoseskilled in the art will understand that a computer-readable medium 1030on which is a computer program 1032 for simultaneous radio detection andbearing determination may be provided to the computer system 1000. Theform of the medium 1030 and language of the program 1032 are understoodto be appropriate for computer system 1000. Utilizing the memory stores,such as for example one or more hard drives 1014 and main system memory1012, the operable CPU 1002 will read the instructions provided by thecomputer program 1032 and operate to perform the scheduling system 100as described above.

Moreover in at least one embodiment, aspects of the method, such as theapplication of the FFT to the time domain snapshot to provide theFrequency Spectrum, the comparison of the spectrum to a threshold andthe corresponding identification of signals breaching the threshold, theadjustment of the threshold, the computation of bearing, and/or therecording and outputting of the determined information to a data storagedevice, remote location or both are operations enabled as executableinstructions for a computer enabled system, e.g. processor 158. Thecontemporaneous transformation of one or more detected radio signalswithin a given frequency domain into a quantified bearing, frequency andaudio recording of the transmission is a highly advantageous ability ofSRDBS 100.

Changes may be made in the above methods, systems and structures withoutdeparting from the scope hereof. It should thus be noted that the mattercontained in the above description and/or shown in the accompanyingdrawings should be interpreted as illustrative and not in a limitingsense. The following claims are intended to cover all generic andspecific features described herein, as well as all statements of thescope of the present method, system and structure, which, as a matter oflanguage, might be said to fall therebetween.

1. A simultaneous radio detection and bearing system, comprising: an RFconditioning subsystem having a plurality of arrays of Frequency Rangesignal receiving channels, the RF conditioning subsystem operable tocombine the signals from the arrays as a first internal data stream; acoherent multi-channel digitizer subsystem coupled to the RFconditioning system, the coherent multi-channel digitizer subsystemoperable to generate a time domain snapshot of the first internal datastream; an audio recording subsystem coupled to the RF conditioningsubsystem; and a processor coupled to the coherent multi-channeldigitizer subsystem and the audio recording subsystem, the processoroperable to transform the time domain snapshot to a frequency spectrumand identify at least one signal above a threshold at a determinedfrequency, determine the bearing of the signal, and provide thedetermined frequency of a selected identified signal to the audiorecording subsystem, the audio subsystem contemporaneously recording theselected signal upon the determined frequency.
 2. The simultaneous radiodetection and bearing system of claim 1, having an array of FirstFrequency Range signal receiving channels and an array of SecondFrequency signal receiving channels.
 3. The simultaneous radio detectionand bearing system of claim 2, having an at least one additional arrayof Third Frequency Range signal receiving channels.
 4. The simultaneousradio detection and bearing system of claim 1, wherein each array ofFrequency Range signal receiving channels is different and each isselected from the group consisting of LF, MF, HF, VHF, UHF, SHF, EHF andcombinations thereof.
 5. The simultaneous radio detection and bearingsystem of claim 1, wherein the simultaneous radio detection and bearingsystem is portable.
 6. A simultaneous radio detection and bearingsystem, comprising: an RF conditioning subsystem having a plurality ofFirst Frequency Range and Second Frequency Range signal receivingchannels, the RF conditioning subsystem operable to combine FirstFrequency Range and Second Frequency Range signals as a first internaldata stream; a coherent multi-channel digitizer subsystem coupled to theRF conditioning system, the coherent multi-channel digitizer subsystemoperable to generate a time domain snapshot of the first internal datastream; an audio recording subsystem coupled to the RF conditioningsubsystem; and a processor coupled to the coherent multi-channeldigitizer subsystem and the audio recording subsystem, the processoroperable to transform the time domain snapshot to a frequency spectrumand identify at least one signal above a threshold at a determinedfrequency, determine the bearing of the signal, and provide thedetermined frequency of a selected identified signal to the audiorecording subsystem, the audio subsystem contemporaneously recording theselected signal upon the determined frequency.
 7. The simultaneous radiodetection and bearing system of claim 6, wherein the RF conditioningsubsystem includes an array of at least four First Frequency Rangeantennas and an array of at least four Second Frequency Range antennas,arranged as concentric squares.
 8. The simultaneous radio detection andbearing system of claim 6, wherein the First Frequency Range channelsinclude active antennas.
 9. The simultaneous radio detection and bearingsystem of claim 6, wherein the RF conditioning subsystem is a receiverand block down converter, the first internal data stream being an analogintermediate frequency signal.
 10. The simultaneous radio detection andbearing system of claim 6, wherein the RF conditioning subsystem is adigital receiver and filter, the first internal data stream being adigital signal.
 11. The simultaneous radio detection and bearing systemof claim 6, wherein for a detected signal each detecting channel has arespective phase of the signal, the bearing determined by a best matchprocess of comparing each respective phase to a database of calibrationvalues for three hundred and sixty degrees of bearings.
 12. Thesimultaneous radio detection and bearing system of claim 6, wherein theFirst Frequency Range signal receiving channels and the Second FrequencyRange signal receiving channels are different and each is selected fromthe group consisting of LF, MF, HF, VHF, UHF, SHF, EHF and combinationsthereof.
 13. The simultaneous radio detection and bearing system ofclaim 6, wherein the First Frequency Range is the VHF frequency rangeand the Second Frequency Range is the UHF frequency range.
 14. Thesimultaneous radio detection and bearing system of claim 6, wherein thesystem is operable to detect UHF signals in a range of about 462 MHz˜467MHz and VHF signals in a range of about 138 MHz˜174 MHz.
 15. Thesimultaneous radio detection and bearing system of claim 6, furtherincluding a sustainable power supply.
 16. The simultaneous radiodetection and bearing system of claim 15, wherein the sustainable powersupply is a solar array.
 17. The simultaneous radio detection andbearing system of claim 6, further including a GPS subsystem and digitalcompass, the bearing of the signal determined with reference to a GPSdetermined position and digital compass reference axis.
 18. Thesimultaneous radio detection and bearing system of claim 6, wherein thesimultaneous radio detection and bearing system is portable.
 19. Thesimultaneous radio detection and bearing system of claim 6, wherein thesystem is camouflaged.
 20. The simultaneous radio detection and bearingsystem of claim 6, wherein the system is about twenty inches square byabout 6 inches high.
 21. The simultaneous radio detection and bearingsystem of claim 6, wherein a plurality of radio detection and bearingsystems permits contemporaneous determination of an identified signallocation in addition to frequency and bearing.
 22. A simultaneous radiodetection and bearing system, comprising: an RF receiver and block downconverter subsystem operable to receive First Frequency Range and SecondFrequency Range signals on at least four channels and provide a combinedintermediate analog frequency signal; a coherent multi-channel digitizersubsystem coupled to the receiver and block down converter subsystem,the coherent multi-channel digitizer subsystem operable to receive thecombined intermediate analog frequency and render a time domain snapshotfor the frequency domain; a processor coupled to the coherentmulti-channel digitizer subsystem, the processor operable to transformthe time domain snapshot to a frequency spectrum and identify at leastone signal at a determined frequency and contemporaneously determine thebearing of the signal based on a comparison of signal phase establishedby the coherent multi-channel digitizer; and an audio recordingsubsystem coupled to the receiver and block down converter subsystem andthe processor, the audio subsystem operable to demodulate and record anaudio signal from the analog intermediate frequency signal on thedetermined frequency provided by the processor.
 23. The simultaneousradio detection and bearing system of claim 22, wherein the receiver andblock down converter subsystem includes at least four First FrequencyRange and four Second Frequency Range antenna arrays arranged asconcentric squares.
 24. The simultaneous radio detection and bearingsystem of claim 23, wherein the four First Frequency Range antennas areactive antennas.
 25. The simultaneous radio detection and bearing systemof claim 22, wherein the audio recording subsystem includes a pluralityof simultaneously operable radios.
 26. The simultaneous radio detectionand bearing system of claim 22, wherein the multi channel digitizer isprovided by two coherent dual channel digitizers.
 27. The simultaneousradio detection and bearing system of claim 22, wherein for a detectedsignal each detecting channel has a respective phase of the signal, thebearing determined by a best match process of comparing each respectivephase to a database of calibration values for three hundred and sixtydegrees of bearings.
 28. The simultaneous radio detection and bearingsystem of claim 22, wherein the First Frequency Range is the VHFfrequency range and the Second Frequency Range is the UHF frequencyrange.
 29. The simultaneous radio detection and bearing system of claim22, wherein the system is operable to detect UHF signals in a range ofabout 462 MHz˜467 MHz and VHF signals in a range of about 138 MHz˜174MHz.
 30. The simultaneous radio detection and bearing system of claim22, further including a sustainable power supply.
 31. The simultaneousradio detection and bearing system of claim 22, wherein a plurality ofradio detection and bearing systems permits contemporaneousdetermination of an identified signal location in addition to frequencyand bearing.
 32. A method of simultaneous radio detection and bearing,comprising: providing an RF receiver and conditioning subsystem havingat least four First Frequency Range channels and Second Frequency Rangechannels; sampling the First Frequency Range and Second Frequency Rangespectrum each in a predetermined range; converting the samples into afirst internal data stream; simultaneously providing the internal signalto a digitizer subsystem and an audio recording subsystem; digitizingthe internal signal at predetermined intervals to provide a time domainsnapshot; transforming the time domain snapshot with a FFT to provide afrequency spectrum; and comparing the frequency spectrum to a thresholdto identify keyed signals; in response to at least one identified keyedsignal, determining the frequency of the signal and the bearing of thesignal about simultaneously, and for a selected identified signal,engaging the audio subsystem to demodulate the internal signal at thedetermined frequency and record the selected identified signal, therecording of the signal being and the determination of bearing beingabout contemporaneously; and outputting the identified signal frequency,bearing and selected signal recording.
 33. The method of claim 32,wherein selection of an identified signal is based on availability of aradio in the audio subsystem.
 34. The method of claim 32, whereinselection of an identified signal is based on a priority determinationof the identified signal.
 35. The method of claim 32, wherein thepriority determination is based on at least one factor selected from thegroup of, signal strength, a priority frequency, past frequency of use,and combinations thereof.
 36. The method of claim 32, wherein for adetected signal each detecting channel has a respective phase of thesignal, the bearing determined by a best match process of comparing eachrespective phase to a database of calibration values for three hundredand sixty degrees of bearings.
 37. The method of claim 32, wherein thefirst internal data stream is an analog intermediate frequency signal.38. The method of claim 32, wherein the first internal data stream is adigital signal.
 39. The method of claim 32, wherein the output of theidentified signal frequency, bearing and recording is stored to adatabase.
 40. The method of claim 32, wherein the First Frequency Rangeis the VHF frequency range and the Second Frequency Range is the UHFfrequency range.
 41. The method of claim 32, wherein the method isoperable to detect UHF signals in a range of about 462 MHz˜467 MHz andVHF signals in a range of about 138 MHz˜174 MHz.
 42. The method of claim32, wherein the method is performed by interconnected componentsincluding: an RF conditioning subsystem having a plurality of FirstFrequency Range and Second Frequency Range signal receiving channels,the RF conditioning subsystem operable to combine First Frequency Rangeand Second Frequency Range signals as a first internal data stream; acoherent multi-channel digitizer subsystem coupled to the RFconditioning system, the coherent multi-channel digitizer subsystemoperable to generate a time domain snapshot of the first internal datastream; an audio recording subsystem coupled to the RF conditioningsubsystem; and a processor coupled to the coherent multi-channeldigitizer subsystem and the audio recording subsystem, the processoroperable to transform the time domain snapshot to a frequency spectrumand identify at least one signal above a threshold at a determinedfrequency, determine the bearing of the signal, and provide thedetermined frequency of a selected identified signal to the audiorecording subsystem, the audio subsystem contemporaneously recording theselected signal upon the determined frequency.
 43. The method of claim32 performed by a plurality of radio detection and bearing systems eachin a different location, the determined bearings permitting thedetermination of a location for each detected signal.